As a liquid crystal display device type, so-called TN type, STN type, OCB type, HAN type, VA type (PVA type and MVA type), IPS type or the like are well known. Among them, the IPS (In-Plane Switching) mode liquid crystal display device (hereinbelow, also simply referred to as “IPS liquid crystal display device) has a liquid crystal cell having a liquid crystal layer and a pair of substrates which sandwich the liquid crystal layer, polarizing plates each arranged at both sides (that is, viewing side and back light side) of the liquid crystal cell. The IPS liquid crystal display device is now widely used for a portable device such as a tablet type display device or a smart phone. In an IPS liquid crystal display device, liquid crystal molecules that are contained in a liquid crystal layer for black display are oriented in parallel to the surface of a pair of substrates, and thus the IPS liquid crystal display device has an advantage of having excellent black display performance. The IPS liquid crystal display device also has an advantage of ensuring high viewing angle at certain level even without using a so-called optical compensation film (that is, viewing angle widening film). Meanwhile, there is a problem that, from the viewpoint of optical characteristics of a liquid crystal cell provided in the IPS liquid crystal display device, optical leak occurs when an image is viewed in tilt direction so that contrast of a display image is lowered.
In a liquid crystal display device, a phase difference film is generally used for the purpose of preventing a decrease in contrast. However, for further improving the performances, a phase difference film capable of responding to various optical designs is required. Further, it is more strongly required for a phase difference film mounted in a portable device like those described above to have thin film profile and light weight characteristics.
As a general method for producing a phase difference film, there is a method of producing a polymer film based on monoaxial stretching or biaxial stretching by using various stretching methods. However, because the phase difference exhibited by stretching is dependent on the optical characteristics of a polymer, there is a limit for controlling the exhibition of phase difference only by a stretching technique.
For a phase difference film used in an IPS liquid crystal display device, for example, it is required that “in-plane retardation (Ro) value is high and thickness-direction retardation (Rt) value is small.” However, when a stretching treatment is performed for increasing the in-plane retardation (Ro) value, the thickness-direction retardation (Rt) value also increases so that it becomes difficult to produce a phase difference film simultaneously having desirable in-plane phase difference and desirable thickness-direction phase difference.
In this connection, a method of exhibiting a desired phase difference value by having a laminated phase difference film with constitution in which plural phase difference films are laminated has been suggested (see, Patent Literature 1). However, the laminated phase difference film has a problem in re-workability of a process of producing a liquid crystal display device. Specifically, there is a problem of having a great amount of production loss when an attached film is peeled and attached again or the like, because clean peeling is not achieved.
In this connection, for the purpose of improving the re-workability of a laminated phase difference film, a method of enlarging area of a film in contact with the opposite side of a liquid crystal cell is suggested (see, Patent Literature 2). According to this method, however, the peeling is easy at the beginning but it becomes difficult from the middle, and thus a problem of having peeling residues still remains unsolved.